Process of separating tantalum from niobium



United States Patent Ofice Patented July. 5,. 1960 PROCESS OF SEPARATING'TANTAIZUM FROM NIOBIUM.

Lloyd H. Brown, Crystal Lake, and Francis Cole, Woodstock; Ill.,-assignors to The Quaker Oats Conipany, Chicago, 111., a corporation of New Jersey N'o Drawing. Filed Dec. 2, 1957, Ser. No. 699,882

5 Claims. (Cl. 23-23) This invention relates to the recovery of tantalum values from aqueous solutions and particularly to the separation of tantalum hydroxide from niobium hydroxide by solvent extraction.

Tantalum and niobium are found together in many ores, for example, in the columbite-tantalite type ores. These are oxidic ores containing tantalum and niobium as pentoxides largely in association with vferrous oxide and manganous oxide. Other sources of both niobium and tantalum include the ore fergusonite and the residues obtained in processing blomstradine.

Tantalum finds many uses in metallurgy particularly as a component of alloys. It is usually desirable to incorporate the tantalum in a pure form and consequently there is need for a process whereby tantalum can be effectively separated from niobium. Since tantalum and niobium are in the same group of the periodic table they have similar chemical properties and separation of the two elements has not been easily accomplished. Some of the methods employed in the prior art require the use of highly toxic and corrosive reagents such as hydrofluoric acid.

One of the objects of this invention is to provide a process by which niobium values and tantalum values can be easily and effectively separated fi'om each other.

Another object of this invention is to provide a process for separating tantalum from niobium which does not require the use of highly toxic and corrosive reagents such as hydrofluoric acid.

According to the invention the aforementioned objects are accomplished by preparing the hydroxides of the niobium and tantalum values, dissolving the hydroxides in an aqueous solution of a furfural-soluble alpha-hydroxy acid, contacting the acid solution containing the values with furfural and separating a furfural preferentially tantalum-containing phase from an aqueous niobium-containing phase.

The alpha-hydroxy acid employed preferably has a maximum of nine carbon atoms. Such acids generally have the formula RCHOH-COOH wherein R is hydrogen, alkyl, furyl or aryl, or have the general formula HOOC-CHOH(CH CHOH-COOH wherein n equals an integer from to 5 inclusive. Suitable acids fitting the above description include glycolic acid, lactic acid, tartaric acid, and homologues thereof.

To prepare hydroxides of the niobium and tantalum values from ores containing the values as oxides, any of the known conventional procedures may be employed. For example the ore may be extracted with a mineral acid such as hydrochloric acid, or the ore may be fused with an alkali such as sodium hydroxide. The latter procedure produces the meta-tantalate and meta-niobate which are then decomposed with mineral acid to give the metal hydroxides.

In a preferred embodiment of the invention the ore containing tantalum and niobium values is fused with sodium hydroxide or other alkali to produce the alkali metal nicbate and tantalate. The tantalates are treated tion of one or theoth'er aforedescribed:alphashydroxy acids.= These acids:- act as chelating agents, and the amount employed is any amount sufiieientttol completely dissolve the hydroxides. For economic reasons no more than necessary is employed. The latter acid solution is shaken with furfural which preferably has been equilibrated with an aqueous solution of alpha-hydroxy acid of the same strength as that used in dissolving the hydroxides. This insures that the furfural and water will contain an equilibrium quantity of glycolic acid before and after the extraction, i.e., that the glycolic acid concentration will not change in either aqueous or furfural phase. The two phases are separated and if desired may be stripped with fresh solvent or solution. The liquid is boiled ofi? or distilled from each of the phases and the residue ignited to recover the tantalum and niobium values as oxides. Alternatively, chemical procedures may be used to precipitate the values from the two phases.

The invention will be further illustrated but is not limited by the following examples in which the quantities are stated in parts by weight unless otherwise indieated:

Example 1 A mixture of oxides consisting of 117 parts niobium and 71 parts of tantalum are fused with sodium hydroxide. After the melt cools it is dissolved in Water. An excess of dilute hydrochloric acid is then added to the solution precipitating the hydroxides. The hydroxide precipitate is filtered, washed with water and dissolved in 20,000 parts of an aqueous glycolic acid solution (about 3.5 molar). The glycolic acid solution is then shaken with an equal volume of furfural which has been previously equilibrated with the same glycolic acid solution. When the two phases have separated the aqueous layer is decanted and the water removed by boiling. The residue obtained is ignited. On analysis it is found to contain about 67 parts of NbO and about 21 parts of TaO The furfural in the remaining bottom layer is distilled off and the residue ignited. This residue analyzes about 50 parts N-b0 and about 50 parts TaO- Example 2 The procedure of Example 1 is repeated with the exception that the starting material contains 146 parts of tantalum oxide and 140 parts of niobium oxide. The ignited residue obtained from the aqueous phase analyzes about 26 parts Ta0 and about 76 parts NbO The ignited residue from the furfural phase analyzes about 120 parts Ta0 and about 64 parts NbO Example 3 The procedure of Example 1 is repeated with the exception that the starting material contains 69 parts of tantalum oxide and 191 parts of niobium oxide. The ignited residue obtained from the aqueous phase analyzes about 21 parts TaO and about 96 parts of NbO The ignited residue from the furfural phase analyzes about 48 parts of TaO and about parts of NbO From the above examples it is evident that tantalum values are effectively separated from niobium values from various mixtures of the two in oxide form. Substantially complete separation of niobium from tantalum is obtainable by repeated extractions with fresh furfural or fresh alpha-hydroxy acid solution prior to recovery of the residues.

We claim: 3. Tbs process of claim 1 in which the alpha-hydroxy 1. A process for separating tantalum values from acid is lactic acid. niobium values contained in a mixture of the hydroxides 4, The process of claim 1 in which the alpha-hydroxy thereof, comprising dissolving the hydroxides in an aqueous solution of a furfural-soluble alpha-hydroxy acid 5 selected from the group consisting of glycolic acid, lactic acid, and tartaric acid; mixing the acid solution containing Said Values with fillfural; and sfiparatiflg a fIJIfllIal' References Cited in the file of this patent phase preferentially containing tantalum values from an UNITED STATES PATENTS aqueous phase containing niobium values. 10

2. The process of claim 1 in which the alpha-hydroxy 1,802,242 Pink 61 P 1931 acid is glycolic acid. 2,773,737 Nielsen et al. Dec. 11, 1956 acid is tartaric acid.

5. The process of claim 1 in which the aqueous solution of acid is about 3.5 molar glycolic acid. 

1. A PROCESS FOR SEPARATING TANTALUM VALUES FROM NIOBIUM VALUES CONTAINED IN A MIXTURE OF THE HYDROXIDES THEREOF, COMPRISING DISSOLVING THE HYDROXIDES IN AN AQUEOUS SOLUTION OF A FURFURAL-SOLUBLE ALPHA-HYDROXY ACID SELECTED FROM THE GROUP CONSISTING OF GLYCOLIC ACID, LACTIC ACID, AND TARTARIC ACID, MIXING THE ACID SOLUTION CONTAINING SAID VALUES WITH FURFURAL, AND SEPARATING A FURFURAL PHASE PREFERENTIALLY CONTAINING TATALUM VALUES FROM AN AQUEOUS PHAE CONTAINING NIOBIUM VALUES. 